Sheldon: New topic: women. Delightfully mysterious or bat-crap crazy?

Amy: Goodnight, Stuart.
Stuart: Goodnight.
*Stuart and Amy hug*
Sheldon: (From inside Amy's apartment) Take the hint, Stuart, the lady said goodnight!

Sheldon: Amy Farrah Fowler has asked me to meet her mother.
Leonard: Yeah, so?
Sheldon: What does that mean?
Leonard: Well, you know how you're always saying Amy is a girl who is your friend but not your girlfriend?
Sheldon: Uh huh.
Leonard: Well, you can't say that any more.

Sheldon: Would you like some aloe vera? 'cause you just got burned.

Sheldon: You know, I do recall seeing some female undergarments. Where was that? Oh, yes. Earlier this evening, I happened to gaze out the window and a brassiere caught my eye. Do those look familiar?

Sheldon: Einstein defined insanity as doing the same thing over and over again and expecting different results. By that definition, Penny is cuckoo for Cocoa Puffs.

Sheldon: As a native Texan, I must say I've never heard the phrase "yeeehaw" used in quite that context.

Leonard: Well you don't have to worry, we broke up again.
*Sheldon gives awkward look and then throws his papers in the air with one of them landing next to his head.
Sheldon: Do you ever think about other people, Leonard? Do you?

Sheldon: I've never said these words before, but good job, Howard.

Sheldon: I know he (Spock) wouldn't care for an outburst of human emotion, but oh goodie, oh goodie, oh goodie!

Howard: Okay, here it is. Bernadette said you guys are all sick of me talking about my trip to space. Is that true?
Sheldon: Yes.
Raj: No.
Sheldon: We seem to have different approaches here. I was going for helpful honesty. I have no idea what you're doing.
Raj: It's called being nice.
Sheldon: Okay. If you think being nice will get him to shut up, I'll try it.

Sheldon: What are you doing here?
Howard: I've been up all night. I had a fight with Bernadette.
Sheldon: Why?
Howard: She bought me a nice watch.
Sheldon: Leonard, do you understand any of this?
Leonard: Yes.
Sheldon: Talk to him.

Sheldon: Hello. Well, this seems like an odd time to test my cell phone quality but go on. Test phrases. All right. Imatote. Ulba. Twad. All together? All right. I'm a total butt wad. Why are you laughing? Hello?
Penny: And that girls is how you make a phony phone call.

Sheldon: Yes, since their relationship became carnal, Penny has updated his designated term of endearment, distinguishing him from those she calls 'sweetie,' usually as an attempt to soften a thinly-veiled insult.
Penny: You're boring people, sweetie.
Sheldon: Although sometimes, she omits the veil entirely.

Howard: Are you familiar with the Drake Equation?
Sheldon: The one that estimates the odds of making contact with extraterrestrials by calculating the product of an increasingly restrictive series of fractional values such as those stars with planets, and those planets likely to develop life? N equals R times FP times NE times FL times FI times FC times L?
[pause]
Howard: Yeah, that one.